1. Field of the Invention
The present invention relates to a method for producing a Group III nitride semiconductor light-emitting device, the method having a feature in the way in which a p-pad electrode and an n-electrode are formed.
2. Description of the Related Art
Conventional Group III nitride semiconductor light-emitting devices with a face-up configuration include a p-pad electrode and an n-electrode that are composed of different materials. When such light-emitting devices are produced, a p-pad electrode is formed and then an n-electrode is formed.
Alternatively, there is also a method of simultaneously forming a p-pad electrode and an n-electrode and the method is disclosed in Japanese Unexamined Patent Application Publication No. 2007-158262. In this method, a metal thin film composed of Ni/Au is simultaneously formed on a p-type layer and an n-type layer; the resultant structure is heat treated; a p-pad electrode and an n-electrode that are composed of Ti/Au are simultaneously formed on the metal thin film; and the resultant structure is again heat treated. With this method, Ni is diffused into the n-type layer and hence the contact resistance between the n-type layer and the n-electrode can be decreased. Additionally, the p-pad electrode and the n-electrode are simultaneously formed and hence the production steps can be simplified.
A Group III nitride semiconductor light-emitting device with a face-up configuration is desirably produced such that, since a p-pad electrode does not allow light to pass therethrough, a region of an active layer right below the p-pad electrode does not emit light, thereby increasing the light-emitting efficiency of the light-emitting device. Techniques for forming such a region are disclosed, for example, in Japanese Unexamined Patent Application Publication Nos. 10-229219, 10-144962, and 2000-124502.
In the technique disclosed in Japanese Unexamined Patent Application Publication No. 10-229219, a transparent electrode composed of a metal thin film is formed on a p-type layer; a p-pad electrode containing a metal that reacts with nitrogen is formed on the transparent electrode; the resultant structure is heat treated so that the metal contained in the p-pad electrode reacts with nitrogen in the p-type layer, thereby generating nitrogen vacancy in the p-type layer to form a high-resistance region. The presence of this high-resistance region in the p-type layer makes a region of an active layer right below the p-pad electrode emit no light.
Alternatively, the region of the active layer right below the p-pad electrode is made to emit no light by forming an n-type layer between the p-pad electrode and the p-type layer in accordance with the technique disclosed in Japanese Unexamined Patent Application Publication No. 10-144962, or by forming an insulation film such as SiO2 between the p-pad electrode and the p-type layer in accordance with the technique disclosed in Japanese Unexamined Patent Application Publication No. 2000-124502.